The foregoing U.S. Pat. No. 4,384,797 to Anderson et al is directed generically to this lift-off correction at intermediate temperatures. Subsequent enhancements to such lift-off correction are described in the prior art. For example, U.S. Pat. No. 4,545,693 to Bartlett et al, discloses and claims employing a series of pulses to effect the lift-off correction.
Resistive ribbon printing from a ribbon suitable for lift-off correction is subject to being rubbed off the paper on which it is printed. Actual abrasion resistance depends upon the overall system involved, including the characteristics of the thermal ink, the manner of printing, and the characteristics of the paper or other substrate printed upon. A general improvement of abrasion resistance for such systems permits a wider use of thermal printing and is a factor permitting other elements of the system to be modified as may be desirable.
This invention employs moderate heating subsequent to printing to modify the resistance of printed characters to rubbing and other abrasion and to modify the appearance of the printed characters. The heated printing is typically darker and appears heavier. Surprisingly, such moderate heating does not destroy the quality of being capable of lift-off correction, and the heat is therefore applied after printing without regard to the fact that a subsequent lift-off erase operation may be conducted. U.S. Pat. No. 2,057,696 to Sherman shows general heating of a transfer medium to facilitate printing. This description has no indication of the possibility of lift-off correction. Heat fixing in copier technology is a post imaging step to harden an ink image.